1. Field of the Invention
The present invention relates to apparatuses for the detection of electrical corona discharge.
2. Description of the Related Art
High-voltage electrical apparatus often are surrounded by a corona which is discharged by the apparatus when the surrounding air begins to lose insulating qualities. For example, apparatus such as electrical power transmission lines, transformer and substation insulators and bushings, high-voltage power supplies, and the like often have coronas associated therewith when the high electric field of the device causes the surrounding air to begin to conduct rather than insulate. Thus, it is desirable to detect the position and extent of such coronas in order to detect and address equipment failure. These coronas, which are also sometimes referred to as corona discharges, will be referred to herein simply as coronas.
Such coronas are typically most easily visible or detectable by various techniques in darkness. However, there is a need to be able to detect coronas even when there is not complete darkness, i.e. when there is ambient light such as sunlight or artificial indoor light. One technique used to detect and identify the general position of coronas involves the use of ultrasonic microphones. However, ultrasonic microphones do not provide an image and thus cannot precisely locate the source of most corona discharges.
Conventional night-vision equipment which incorporates image intensifier tubes is also sometimes used to locate corona discharges, and can be used to provide an image of a corona, in addition to detecting the corona, unlike ultrasonic techniques. Unfortunately, conventional night-vision equipment has relatively poor sensitivity to the optical energy emitted by a corona discharge, and much better sensitivity to both sunlight and artifical lighting, requiring the equipment to be operated in virtually complete darkness and giving poor sensitivity to corona. This is inconvenient and expensive.
There is, therefore, a need for improved corona detection techniques.